When shoes, in particular sports shoes, are manufactured, one objective is to restrict the movements of a wearer of the shoe as little as possible. On the other hand, the different loads that arise on the skeleton and the muscles during running should be moderated to reduce fatigue or the risk of injuries under long lasting loads. One cause of premature fatigue of the joints or the muscles is the misorientation of the foot during a step cycle. Typically, professional athletes run exclusively on their forefoot, in particular during track and field events; however, the average amateur athlete first contacts the ground with the heel and subsequently rolls-off using the ball of the foot.
Under a correct course of motion, most athletes perform a slight turning movement of the foot from the outside to the inside between the first ground contact with the heel and the pushing-off with the ball. Specifically, at ground contact, the athlete's center of mass is more on a lateral side of the foot, but shifts to a medial side during the course of the step cycle. This natural turning of the foot to the medial side is called pronation. Supination, i.e., the turning of the foot in the opposite direction, as well as excessive pronation, can lead to increased strain on the joints and premature fatigue or even injury. Therefore, when designing shoes, in particular sports shoes, it is desirable to precisely control the degree of turning of the foot during a step cycle in order to avoid the above-mentioned misorientations.
There are a number of known devices that influence pronation. For example, supporting elements may be placed in the midfoot and the forefoot areas of a sole to avoid excessive turning of the foot to the medial and/or to the lateral side during push-off. Typically, the heel portion of these soles is a simple cushioning element serving only to absorb the arising ground reaction forces. This approach, however, fails to recognize that the first phase of a step cycle influences the later course of motion of the foot. When the foot terminates the ground-contacting phase in the correct orientation prior to transitioning to the pushing-off phase, an essential requirement for an overall correct course of motion is obtained.
It is, therefore, an object of the present invention to provide a shoe sole that leads to a correct orientation of the foot starting from the first ground contact, thereby reducing or eliminating premature fatigue or wear of the joints and the muscles.